In drilling an oil well, the drill bit theoretically cuts a round hole which is advanced into the earth. In practice, the hole is never quite perfectly round, and, moreover, the drill bit will drift occasionally, thereby forming a deviated well. In many instances, these deviations are not important. However, they do create problems when they become extreme. Such problems arise as, for example, in the drifting of a drill bit whereby the drill string above the drill bit works over against the wall of the drilled hole. This can become extreme, even to the point where the drill string will stick. Sticking ordinarily occurs in the drill collars, not in the drill pipe, because the drill collars are slightly larger in diameter. The present invention is an apparatus to be incorporated in the drill string, perhaps at two or three locations, so that the drilled hole can be enlarged, thereby permitting obstructions to be cut away through use of the present invention. It has, therefore, as one feature a means which abrades the previously drilled hole to enlarge the hole slightly at obstructions which rub against the drill string, particularly in the area of the drill collars.
The present invention is particularly advantageous in that it includes means which aligns the apparatus with the hole. As the drill string advances, each joint in the drill collars can be deflected slightly. The present invention features means which cut away the nearest obstruction to the drill collars so that hanging of a drill collar is markedly reduced. This apparatus, therefore, encounters such an obstruction, is guided into operative contact with the obstruction and cuts into the obstruction as the drill string is rotated and advanced. One embodiment of the present invention incorporates a bottom spiral of several turns which aligns the remainder of the hole straightening apparatus with the obstruction by feeding in the bottom helical thread on the tool. This embodiment utilizes hardfacing material on the thread.
An alternate embodiment of the present invention utilizes flutes at the bottom of the hole straightening apparatus. The bottom located flutes align the hole straightening apparatus with the hole as it first enters the deviated area. Moreover, annular clearance is permitted through the flutes for the mud return flow path adjacent to the drill string. Thus, the mud flow passes through the flutes and parallel to the face of the hole straightening apparatus. This enables the deviated area to be straightened with a minimum of difficulty.
With the foregoing in mind, this apparatus is briefly summarized as hole straightening apparatus utilizing an elongate tubular member having a square cross section. The square cross section extends the greater portion of the length, thereby defining four corners. The four corners are rounded, that is to say, they are arcuately shaped and surfaced with hardfacing material. At the lower end, straight flutes, helical flutes or a spiral thread is incorporated to advance the tool into the deviated area of the well. They are also equipped with hardfacing material.